By default Enterprise Linux 7 comes with Postfix 2.10. To take advantage of new features that come with Postfix 3 such as SMTPUTF8 support, you can use the rpm packages in my yum repository. This article will take you through the steps to install Postfix 3.3 on CentOS or Red Hat Enterprise 7.
First get started by adding a new yum repository to your system.
Add the file /etc/yum.repos.d/postfix.repo and add the following lines:
name=EL-$releasever Postfix repo
Now import the public key used for the signing of the rpms:
Add the following line to the [base] and [update] sections of /etc/yum.repos.d/CentOS-Base.repo to exclude postfix packages from the default repository.
Now you can upgrade your Postfix package by performing a yum update.